Blue colored heat treatable coated article having low solar factor value

ABSTRACT

There are provided coated articles that include two or more infrared (IR) reflecting layers (e.g., of or including NbZr, Nb, NiCr, NiCrMo, and/or a nitride thereof) sandwiched between at least dielectric layers, and/or a method of making the same. The coating may be designed so that the coated articles realize blue glass side reflective coloration in combination with a low glass side visible reflectance, acceptable film side coloration, and low solar factor (SF) and/or a low solar heat gain coefficient (SHGC). Such coated articles may be used in the context of monolithic windows, insulating glass (IG) window units, laminated windows, and/or other suitable applications, and may optionally be heat treated (e.g., thermally tempered) in certain instances.

This application claims priority on U.S. Provisional Application62/308,266, filed Mar. 15, 2016, the disclosure of which is incorporatedherein by reference.

This invention relates to coated articles that include two or morefunctional infrared (IR) reflecting layers sandwiched between at leastdielectric layers, and/or a method of making the same. The coating maybe designed so that the coated articles realize blue glass sidereflective coloration, low glass side visible reflectivity, andacceptable film side coloration in combination with a low solar factor(SF) and/or low solar heat gain coefficient (SHGC). Such coated articlesmay be used in the context of monolithic windows, insulating glass (IG)window units, laminated windows, and/or other suitable applications, andmay optionally be heat treated (e.g., thermally tempered) in certaininstances.

BACKGROUND AND SUMMARY OF THE INVENTION

Solar control coatings having a layer stack of glass/Si₃N₄/NiCr/Si₃N₄are known in the art, where the metallic NiCr layer is the sole infrared(IR) reflecting layer in the coating. In certain instances, the NiCrlayer may be nitrided. For example, see U.S. Pat. No. 6,926,967, whichis hereby incorporated herein by reference. See also U.S. Pat. No.5,688,585.

Unfortunately, while such layer stacks with NiCr IR reflecting layersprovide efficient solar control and are overall good coatings, they arelacking in terms of being able to achieve a wider palette of availablecolors when desired. For example, with such a coating stack, if bluishgreen is desired the approach is to significantly increase the bottomdielectric thickness which unfortunately results in undesirableinterference effects in that particular coating.

Blue coloration is often desired in the context of monolithic windows,insulating glass (IG) window units, and/or other suitable applications.Desirable blue coloration (e.g., glass side/exterior/outsidereflective), measured monolithically and/or in an IG window unit, may becharacterized by: b* values of from −8.0 to −30.0, more preferably from−11.0 to −19.0, and most preferably −12.0 to −18.0; optionally incombination with a* values of from −7.0 to+7.0, more preferably from−5.0 to +5.0, and most preferably from −3.0 to +2.0.

Low solar factor (SF) and solar heat gain coefficient (SHGC) values arealso desired in some applications, particularly in warm weatherclimates. Solar factor (SF), calculated in accordance with EN standard410, relates to a ratio between the total energy entering a room or thelike through a glazing and the incident solar energy. Thus, it will beappreciated that lower SF values are indicative of good solar protectionagainst undesirable heating of rooms or the like protected bywindows/glazings. A low SF value is indicative of a coated article(e.g., IG window unit) that is capable of keeping a room fairly cool insummertime months during hot ambient conditions. Thus, low SF values aresometimes desirable in hot environments. While low SF values aresometimes desirable for coated articles such as IG window units, theachievement of lower SF values may come at the expense of sacrificingcoloration. It is often desirable, but difficult, to achieve acombination of acceptable visible transmission, desirable glass sidereflective coloration, and a low SF value for a coated article such asan IG window unit or the like. SF (G-Factor; EN410-673 2011) and SHGC(NFRC-2001) values are calculated from the full spectrum (T, Rg and Rf)and are typically measured with a spectrophotometer such as a PerkinElmer 1050. The SF measurements are done on monolithic coated glass, andthe calculated values can be applied to monolithic, IG and laminatedapplications.

U.S. Patent Document 2012/0177899 discloses several different coatings.Examples 1-5 on page four of US '899 areglass/SiN/NiCrNx/SiN/NiCrNx/SiN. However, none of these examples achieveblue glass side reflective coloration, as evidenced by their respectiveglass side reflective (b*_(G)) values outside of the range from −8 to−30. Moreover, these examples suffer from undesirably high SF and SHGCvalues.

U.S. Pat. No. 8,286,395 discloses numerous coatings, but none canaccomplish the features of coatings according to embodiments of thisinvention. The coatings in Comparative Example 1 of US '395 cannotachieve blue glass side reflective color, as evidenced by theirrespective glass side reflective (a*_(G/external)) values outside of therange of from −8 to −30. The coating of Comparative Example 2 in US '395has an undesirably green film side color as evidenced by thea*_(F/internal) value of −4.8. And the counter-examples underComparative Example 2 in US '395 are undesirable in that they have highglass side visible reflectivity values of 22.6% and 21.2%, respectively.Coating Nos. 1-2 in Comparative Example 3 of US '395 are undesirable inthat neither can achieve blue glass side reflective coloration asevidenced by their respective glass side reflective (a*_(G/external))values outside of the range of from −8 to −30, and Coating No. 1 alsohas an undesirably high glass side visible reflectance (RY_(G/out)) of28%. Under Example 3 of US '395, coating No. 3 is undesirable in that itrequires additional titanium (Ti) metal layers, and coating No. 4 has anundesirably high glass side visible reflectance (RY_(G/out)) of 22.3% aswell as an undesirably green film side reflective color as evidenced bythe a*F/internal value of −11.3. Thus, it will be appreciated thatcoatings of US '395 cannot achieve desirable blue glass side reflectivecoloration in combination with low glass side visible reflectivity,acceptable film side coloration, and a low solar factor (SF) and/or lowsolar heat gain coefficient (SHGC). US '395 is silent as to SF and SHGCvalues. It is noted that glass side reflective color is a significantcolor when an IG window unit is provided with the coating on surfacetwo, as the glass side reflective color is the color seen by thoseoutside viewing the building on which the window is mounted.

It would be desirable if blue glass side reflective coloration could beachieved in an efficient manner in combination with low glass sidevisible reflectivity, acceptable film side coloration, and a low solarfactor (SF) and/or low solar heat gain coefficient (SHGC). Note that atypical conventional IG window unit with two panes has an SHGC valuearound 0.70.

In certain example embodiments of this invention, it has surprisinglybeen found that by providing two or more IR reflecting layers (e.g., ofor including NbZr and/or NbZrN_(x)) between respective dielectriclayers, along with particular thickness parameters, desirable blue glassside reflective coloration can be achieved in combination with low glassside visible reflectivity, acceptable film side coloration, and a lowsolar factor (SF) and/or low solar heat gain coefficient (SHGC). Suchcoatings provide for improved color control and/or ranges when desired,low SF values and thus the ability to keep rooms cool in warm climates,and also for good thermal stability (low ΔE* value(s)) if desired.

Generally speaking, certain example embodiments of this inventionfulfill one or more of the above listed needs by providing a coatedarticle having blue glass side reflective coloration and including alayer system supported by a glass substrate, the layer systemcomprising: a first dielectric layer comprising nitrogen; a firstinfrared (IR) reflecting layer on the glass substrate over at least thefirst dielectric layer; a second dielectric layer comprising nitrogen onthe glass substrate over at least the first dielectric layer and thefirst IR reflecting layer; a second layer IR reflecting layer on theglass substrate over at least the second dielectric layer; a thirddielectric layer comprising nitrogen on the glass substrate over atleast the second IR reflecting layer; wherein each of the first andsecond IR reflecting layers comprises one or more of: NbZr, NbZrN_(x),NiCr, NiCrN_(x), NiCrMo, NiCrMoN_(x), NbCr, NbCrN_(x), Nb and NbN_(x);wherein the coated article contains no metallic infrared (IR) reflectinglayer based on Ag and/or Au, and wherein the IR reflecting layers do notphysically contact any other metallic or substantially metallic layer;and wherein the coated article: has glass side visible reflectance of nogreater than 18%, a film side/interior reflective a* color value of −2to +12, glass side/exterior reflective blue coloration comprising aglass side/exterior b* color value of from −8.0 to −30.0; and (i) ifmeasured monolithically has an SF value of no greater than 0.35 and anSHGC value of no greater than 0.40, and/or (ii) if an insulating glass(IG) window unit having two glass substrates has an SF value of nogreater than 0.25 and an SHGC value of no greater than 0.27.

In certain example embodiments of this invention, there is provided acoated article having blue glass side reflective coloration andincluding a layer system supported by a glass substrate, the layersystem comprising: a first dielectric layer comprising silicon nitride;a first infrared (IR) reflecting layer comprising NbZr on the glasssubstrate over at least the first dielectric layer comprising siliconnitride; a second dielectric layer comprising silicon nitride on theglass substrate over at least the first dielectric layer comprisingsilicon nitride and the first IR reflecting layer comprising NbZr; asecond layer IR reflecting layer comprising NbZr on the glass substrateover at least the second dielectric layer comprising silicon nitride; athird dielectric layer comprising silicon nitride on the glass substrateover at least the second IR reflecting layer comprising NbZr; whereinthe coated article contains no metallic infrared (IR) reflecting layerbased on Ag and/or Au, and wherein the IR reflecting layers do notphysically contact any other metallic or substantially metallic layer;and wherein the coated article: has glass side visible reflectance of nogreater than 18%, a film side/interior reflective a* color value of −2to +12, glass side/exterior reflective blue coloration comprising aglass side/exterior b* color value of from −8.0 to −30.0; and (i) ifmeasured monolithically has an SF value of no greater than 0.35 and anSHGC value of no greater than 0.40, and/or (ii) if an insulating glass(IG) window unit having two glass substrates has an SF value of nogreater than 0.25 and an SHGC value of no greater than 0.27.

Thus, this invention covers monolithic window units, IG window units,laminated window units, and any other article including a glasssubstrate having a coating thereon as claimed. Note that monolithicmeasurements may be taken by removing a coated substrate from an IGwindow unit and/or laminated window unit, and then performing monolithicmeasurements. It is also noted that for a given coating the SF and SHGCvalues will be significantly higher for a monolithic window unit thanfor an IG window unit.

In certain example embodiments of this invention, heat treated (HT)coated articles have a glass side reflective ΔE* value due to heattreatment (e.g., thermal tempering) of no greater than 4.5, morepreferably no greater than 4.0, even more preferably no greater than3.5, and most preferably no greater than 3.0. For purposes of example,the heat treatment (HT) may be for at least about 5 minutes at atemperature(s) of at least about 580 degrees C., and is sufficient forthermal tempering. The term ΔE* is known in the art and is indicative ofthermal stability upon heat treatment, and is defined and explained forexample in U.S. Pat. No. 6,926,967 which is incorporated herein byreference.

IN THE DRAWINGS

FIG. 1 is a partial cross sectional view of a monolithic coated article(heat treated or not heat treated) according to an example embodiment ofthis invention.

FIG. 2 is a partial cross sectional view of a monolithic coated article(heat treated or not heat treated) according to another exampleembodiment of this invention.

FIG. 3 is a side cross sectional view of an insulating glass (IG) windowunit, including the coated article of FIG. 1 or FIG. 2, according toexample embodiments of this invention.

DETAILED DESCRIPTION OF CERTAIN EXAMPLE EMBODIMENTS OF THE INVENTION

Referring now more particularly to the accompanying drawings in whichlike reference numerals indicate like parts throughout the severalviews.

Coated articles according to example embodiments of this inventionachieve desirable blue glass side reflective coloration in combinationwith low SF and/or SHGC value(s), and also achieve this in combinationwith optional heat treatability as well as visible glass sidereflectivity of no greater than 18% (more preferably no greater than16%, and even more preferably no greater than 13%), a film sidereflective a* coloration (a*_(F/internal)) of from −2 to +12 (morepreferably from 0 to +8, and most preferably from +1 to +7) in order toreduce green film side coloration, and can do so without needing anyadditional metal layers in addition to provided infrared (IR) reflectinglayers. It has surprisingly been found that by providing two or more IRreflecting layers (e.g., of or including NbZr and/or NbZrN_(x)) betweenrespective dielectric layers, along with particular thicknessparameters, desirable blue glass side reflective coloration anddesirable film side reflective coloration can be achieved in combinationwith a low SF and/or SHGC value and low glass side visible reflectivity.Such coatings provide for improved color control and/or ranges whendesired and low SF values indicating ability to keep rooms cool in warmenvironments, and may also provide for good thermal stability (low ΔE*value(s)) when desired. In example embodiments, the coated article (i)if measured monolithically has an SF value of no greater than 0.35 (morepreferably no greater than 0.33, and most preferably no greater than0.31) and/or an SHGC value of no greater than 0.40, more preferably nogreater than 0.38, and most preferably no greater than 0.36, and/or (ii)if an insulating glass (IG) window unit having two glass substrates hasan SF value of no greater than 0.25 (more preferably no greater than0.23, and most preferably no greater than 0.22 or 0.21) and/or an SHGCvalue of no greater than 0.27 (more preferably no greater than 0.25, andmost preferably no greater than 0.24).

Certain embodiments of this invention provide a coating or layer systemthat may be used in windows such as monolithic windows (e.g., vehicle,residential, and/or architectural windows), IG window units, and/orother suitable applications. Certain example embodiments of thisinvention provide a layer system that is characterized by color control,low SF and/or SHGC values, and/or color stability upon heat treatment.With respect to stability upon heat treatment (HT), this means a lowvalue of ΔE*; where Δ is indicative of a*, b* and L* change in view ofHT such as thermal tempering, heat bending, or thermal heatstrengthening, monolithically and/or in the context of dual paneenvironments such as IG units or laminates. In certain exemplaryembodiments, the color stability with HT may result in substantialmatchability between heat-treated and non-heat treated versions of thecoating or layer system. In other words, in monolithic and/or IGapplications, in certain embodiments of this invention two glasssubstrates having the same coating system thereon (one HT afterdeposition and the other not HT) appear to the naked human eye to looksubstantially the same.

The terms “heat treatment” and “heat treating” as used herein meanheating the article to a temperature sufficient to achieve thermaltempering, heat bending, and/or heat strengthening of the glassinclusive article. This definition includes, for example, heating acoated article in an oven or furnace at a temperature of least about 580degrees C., more preferably at least about 600 degrees C., for asufficient period to allow tempering, bending, and/or heatstrengthening. In certain instances, the HT may be for at least about 4or 5 minutes. The coated article may or may not be heat treated indifferent embodiments of this invention.

FIGS. 1-2 are side cross sectional views of coated articles according todifferent example embodiments of this invention. In the FIG. 1embodiment the solar control coating 8 includes two IR reflecting layers3 and 5, whereas in FIG. 2 the solar control coating 8′ includes threeIR reflecting layers 3, 5 and 15. An additional dielectric layer 16 isalso provided in the FIG. 2 embodiment. FIG. 3 illustrates an IG windowunit, with the coating (8 or 8′) on surface two, showing that the IGwindow unit can use the coating (8 or 8′) of either the FIG. 1embodiment or the FIG. 2 embodiment.

Referring to FIG. 1, the coated article includes at least glasssubstrate 1 (e.g., clear, green, bronze, grey, blue, or blue-green glasssubstrate from about 1.0 to 12.0 mm thick), dielectric layers 2, 4, 6(e.g., of or including silicon nitride (e.g., Si₃N₄), siliconoxynitride, tin oxide, or some other suitable dielectric), IR reflectinglayers 3, 5 which may be of or include substantially metallic ormetallic material such as NbZr, NbZrN_(x), NiCr, NiCrN_(x), NiCrMo,NiCrMoN_(x), NbCr, NbCrN_(x), Nb and/or NbN_(x). It will be appreciatedthat the IR reflecting layers 3 and/or 5 may optionally be nitrided incertain example embodiments of this invention. While the IR reflectinglayers may include some small amount of oxygen in certain instances, itis preferable that these layers 3 and 5 are substantially free of oxygensuch as no more than 5% oxygen, more preferably no more than about 3% or2% oxygen in certain embodiments (atomic %). The coated article furtherincludes dielectric overcoat layer 7 of or including a protectivematerial such as zirconium oxide (e.g., ZrO₂) or silicon oxynitride.Optionally, a dielectric layer of or including silicon oxynitride and/orzirconium silicon oxynitride of any suitable stoichiometry may belocated between and contacting layers 6 and 7 in the upper part of thelayer stack. In certain example embodiments of this invention, coating 8does not include any metallic IR blocking or reflecting layer of orbased on Ag or Au, and the IR reflecting layers 3, 5, 15 do notphysically contact any other metal layers. In certain exampleembodiments of this invention, the IR reflecting layers reflect at leastsome IR radiation, and do not contact any other metal IR reflectinglayer. In certain example embodiments, it is possible for each of thelayers to include other materials such as dopants. It will beappreciated of course that other layers may also be provided, or certainlayers may be omitted, and different materials may be used, in certainalternative embodiments of this invention.

Referring to the FIG. 2 embodiment, the coated article includes at leastglass substrate 1 (e.g., clear, green, bronze, grey, blue, or blue-greenglass substrate from about 1.0 to 12.0 mm thick), dielectric layers 2,4, 6, 16 (e.g., of or including silicon nitride (e.g., Si₃N₄), siliconoxynitride, tin oxide, or some other suitable dielectric), IR reflectinglayers 3, 5, 15 which may be of or include substantially metallic ormetallic material such as NbZr, NbZrN_(x), NiCr, NiCrN_(x), NiCrMo,NiCrMoN_(x), NbCr, NbCrN_(x), Nb and/or NbN_(x). It will be appreciatedthat the IR reflecting layers 3, 5 and/or 15 may optionally be nitridedin certain example embodiments of this invention. Optionally, adielectric layer of or including silicon oxynitride and/or zirconiumsilicon oxynitride of any suitable stoichiometry may be located betweenand contacting layers 16 and 7 in the upper part of the layer stack inthe FIG. 2 embodiment. While the IR reflecting layers may include somesmall amount of oxygen in certain instances, it is preferable that theselayers 3, 5, 15 are substantially free of oxygen such as no more than 5%oxygen, more preferably no more than about 3% or 2% oxygen in certainembodiments. The coated article in FIG. 2 further includes dielectricovercoat layer 7 of or including a protective material such as zirconiumoxide (e.g., ZrO₂) or silicon oxynitride. For example, when the IRreflecting layers are of or include NbZr, they may be sputter depositedusing NbZr targets, and with a gas flow of from about 200-300 ml Ar andfrom about 0.8-2.5 ml/kW N₂ and/or O₂.

In certain example embodiments of this invention, coating 8′ of the FIG.2 embodiment does not include any metallic IR blocking or reflectinglayer of or based on Ag or Au. In certain example embodiments of thisinvention, IR reflecting layers 3, 5 and 15 reflect at least some IRradiation, and do not contact any other metal IR reflecting layer. Incertain example embodiments, it is possible for each of the layers toinclude other materials such as dopants. It will be appreciated ofcourse that other layers may also be provided, or certain layers may beomitted, and different materials may be used, in certain alternativeembodiments of this invention.

The overall coatings (8, 8′) of FIGS. 1-2 include at least theillustrated layers. It is noted that the terms “oxide” and “nitride” asused herein include various stoichiometries. For example, the termsilicon nitride (for one or more of layers 2, 4, 6, 16) includesstoichiometric Si₃N₄, as well as non-stoichiometric silicon nitride.Likewise, various stoichiometries may be used. For instance, when NbZris used for IR reflecting layers 3, 5, 15, various ratios of Nb to Zrmay be used including but not limited to a 50/50 ratio, an 85/15 ratio,or a 90/10 ratio. In certain example embodiments of this invention, theNb/Zr ratio in layers 3, 5, and 15 may be from 1/1 to 9.5/1 in variousexample embodiments of this invention, such that these layers preferablycontain more Nb than Zr. The illustrated layers may be deposited onglass substrate 1 via magnetron sputtering, any other type ofsputtering, or via any other suitable technique in different embodimentsof this invention. It is noted that other layer(s) may be provided inthe stacks shown in FIGS. 1-2 such as between layers 2 and 3, or betweenlayers 3 and 4, or between the substrate 1 and layer 2, or the like.Generally, other layer(s) may also be provided in other locations of thecoating. Thus, while the coating 8, 8′ or layers thereof is/are “on” or“supported by” substrate 1 (directly or indirectly), other layer(s) maybe provided therebetween. Thus, for example, the layer systems 8, 8′ andlayers thereof shown in FIGS. 1-2 are considered “on” the substrate 1even when other layer(s) may be provided therebetween (i.e., the terms“on” and “supported by” as used herein are not limited to directlycontacting). However, there may be the direct contacts shown in FIGS.1-2 in preferred embodiments.

In certain example embodiments of this invention, dielectric layers 2,4, 6, and 16 may each have an index of refraction “n” of from 1.7 to 2.7(at 550 nm), more preferably from 1.9 to 2.5 in certain embodiments, andmost preferably from about 2.0 to 2.06 in preferred embodiments of thisinvention. One, two, three, or all of these layers 2, 4, 6, 16 may be ofor include silicon nitride and/or silicon oxynitride in certain exampleembodiments of this invention. In such embodiments of this inventionwhere layers 2, 4, 6 and/or 16 comprise silicon nitride (e.g., Si₃N₄),sputtering targets including Si employed to form these layers may or maynot be admixed with up to 1-20% (e.g., 8%) by weight aluminum orstainless steel (e.g. SS #316), with about this amount then appearing inthe layers so formed. Even with this amount(s) of aluminum and/orstainless steel, such layers are still considered dielectric layers.

While FIGS. 1-2 illustrate a coated article according to an embodimentof this invention in monolithic form, coated articles according to otherembodiments of this invention may comprise IG (insulating glass) windowunits such as shown in FIG. 3. In IG window embodiments, coating 8 or 8′from FIGS. 1-2 may be provided on the inner wall of the outer substrateof the IG unit as shown in FIG. 3 (surface two), and/or on the innerwall of the inner substrate, or in any other suitable location in otherembodiments of this invention. As shown in FIG. 3, an example IG windowunit may comprise a pair of spaced apart glass substrates 1, 30 eachabout 3-19 mm thick, at least one of which is coated with a coating 8,8′ herein in certain example instances, where the gap 34 between thesubstrates may be from about 5 to 30 mm, more preferably from about 10to 20 mm, and most preferably about 16 mm. Spacer(s) 32 may be providedaround the periphery to space the glass substrates from each other andmaintain gap 34. In certain preferred embodiments, the glass substrate 1shown in FIGS. 1-2 may be the outer glass substrate 1 of an IG windowunit as shown in FIG. 3 and the coating 8, 8′ may be provided on theinterior surface of the outer glass substrate 1 (i.e., surface two ofthe IG window unit). The gap between substrates in an IG unit may befiled with air and/or argon gas in certain example embodiments. IGwindow units having three glass substrates may also be used in exampleembodiments of this invention.

Turning back to the FIG. 1 embodiment, various thicknesses may be usedconsistent with one or more of the needs discussed herein. According tocertain example embodiments of this invention, example thicknesses (inangstroms) and materials for the respective layers of the FIG. 1embodiment on the glass substrate 1 are as follows in certain exampleembodiments for achieving desired blue glass side reflective colorationin combination with a low SF and/or SHGC value(s) and other opticalfeatures (layers are listed in order moving away from the glasssubstrate 1):

TABLE 1 (Thicknesses for blue color and low SF/SHGC in FIG. 1embodiment) Layer Example Range (Å) Preferred (Å) Best (Å) siliconnitride (layer 2): 400-1000 {acute over (Å)}  550-950 {acute over (Å)}650-850 Å IR reflector (e.g., NbZr) 70-160 {acute over (Å)}  90-140{acute over (Å)} 100-130 Å (layer 3): silicon nitride (layer 4): 200-600{acute over (Å)}  300-500 {acute over (Å)} 350-450 Å IR reflector (e.g.,NbZr)  20-90 {acute over (Å)}  35-70 {acute over (Å)}  40-60 Å (layer5): silicon nitride (layer 6): 15-150 {acute over (Å)}  20-100 {acuteover (Å)}  40-80 Å overcoat (e.g., ZrO₂) 10-500 {acute over (Å)}  10-60{acute over (Å)}  20-40 Å (layer 7):

Table 1 above relates to, for example, embodiments where glass sidereflective generally blue coloration and a low SF and/or SHGC value(s)are desirable for the FIG. 1 embodiment (or FIG. 1 embodiment used in anIG window unit as shown in FIG. 3). It has been surprisingly found thatin the FIG. 1 embodiment desirable blue glass side reflective colorationcan be achieved in combination with low SF and low SHGC values, and lowglass side visible reflection and desirable film side reflectivecoloration, using the thicknesses discussed in Table 1 above and whendesigning the FIG. 1 coating 8 so that: (i) bottom dielectric layer 2 isthicker than middle dielectric layer 4 by at least 100 Å, morepreferably by at least 200 Å thicker, and most preferably by at least300 Å; (ii) middle dielectric layer 4 is thicker than dielectric layer 6by at least 100 Å, more preferably by at least 200 Å thicker, and mostpreferably by at least 300 Å; (iii) a thickness ratio of layer 2/layer 6is at least 5, more preferably at least 8, and most preferably at least10; (iv) a thickness ratio of layer 4/layer 6 is at least 3, morepreferably at least 5; and (v) IR reflecting layer 3 is thicker than IRreflecting layer 5 by at least 20 Å, more preferably by at least 30 Å,and most preferably by at least 40 Å. It is noted that desirable bluecoloration (e.g., glass side reflective; typically the same asexterior/outside in a window), measured monolithically and/or in an IGwindow unit, may be characterized by: glass side/exterior/outsidereflective b* values of from −8.0 to −30.0, more preferably from −11.0to −19.0, and most preferably −12.0 to −18.0; optionally in combinationwith a* values of from −7.0 to +7.0, more preferably from −5.0 to +5.0,and most preferably from −3.0 to +2.0.

In certain example embodiments, the IR reflecting layers 3 and 5 may beof the same or substantially the same materials as indicated above(e.g., NbZr and/or a nitride thereof). In certain example embodiments,the layers 3 and/or 5 are metallic, or substantially metallic, and areprovided between nitride layers (e.g., silicon nitride based layers 2,4, 6) in order to reduce or prevent oxidation of the IR reflectinglayers during possible heat treatment (e.g., thermal tempering, heatbending, and/or heat strengthening) thereby permitting predictablecoloration to be achieved following the heat treatment at multipleviewing angles.

In certain exemplary embodiments, the color stability with HT may resultin substantial matchability between heat-treated and non-heat treatedversions of the coating or layer system. In other words, in monolithicand/or IG applications, in certain embodiments of this invention twoglass substrates having the same coating system thereon (one HT afterdeposition and the other not HT) appear to the naked human eye to looksubstantially the same.

Before and/or after any optional heat treatment (HT) such as thermaltempering, in certain example embodiments of this invention coatedarticles according to the FIG. 1 (or FIG. 1, 3) embodiment havecolor/optical characteristics as follows in Table 2 (measured monolithicand/or in an IG unit). It is noted that subscript “G” stands for glassside reflective, subscript “T” stands for transmissive, and subscript“F” stands for film side. As is known in the art, glass side (G) meanswhen viewed from the glass side (as opposed to the layer/film side) ofthe coated article. Film side (F) means when viewed from the side of thecoated article on which the coating is provided. Table 3 set forth belowillustrates certain characteristics of coated articles according tocertain example embodiments of this invention after HT such as thermaltempering (monolithically measured for Table 3) for all colors. Thecharacteristics below in Table 2 are applicable to HT and non-HT coatedarticles herein, except that the thermal stability data in Table 3relates to HT coated articles and demonstrates the stability upon HT.

TABLE 2 Color/Optical Characteristics (FIG. 1 embodiment monolithic orin IG) General Preferred Most Preferred T_(vis) (TY):    8-25%  10-18% 12-17% L*_(T) 30-60 35-55 40-50 a*_(T) −10 to +10 −5 to +5 −3 to +2b*_(T) −10 to +20  −3 to +12  0 to +10 R_(G)Y(glass side): <=18% <=16%<=13% L*_(G) 25-65 30-50 35-45 a*_(G) −7 to +7 −5 to +5 −3 to +2 b*_(G) −8 to −30 −11 to −19 −12 to −18 R_(F)Y(film side): <=35% <=20% <=15%a*_(F)  −2 to +12  0 to +8 +1 to +7 b*_(F) −30 to +30 −22 to +22 −15 to+15 R_(s) (Ω/sq): <140    <100    30-75 SF [Monolithic]: <=0.35 <=0.33<=0.31 SHGC [Monolithic]: <=0.40 <=0.38 <=0.36 SF [IG]: <=0.25 <=0.23<=0.22 or <=0.21 SHGC [IG]: <=0.27 <=0.25 <=0.24

TABLE 3 Thermal Stability (FIG. 1 after HT; in addition to Table 2)General Preferred Most Preferred ΔE*_(G) <=4.0 <=3.5 <=3.0

Regarding the FIG. 2 embodiment, various thicknesses may be usedconsistent with one or more of the needs discussed herein. According tocertain example embodiments of this invention, example thicknesses (inangstroms) and materials for the respective layers of coating 8′ in theFIG. 2 embodiment on the glass substrate 1 are as follows in certainexample embodiments for achieving desired blue glass side reflectivecoloration in combination with a low SF and/or SHGC value(s) and otherdesired optical features (layers are listed in order moving away fromthe glass substrate 1):

TABLE 4 (Thicknesses for blue color and low SF/SHGC in FIG. 2embodiment) Layer Example Range (Å) Preferred (Å) Best (Å) siliconnitride  10-200 {acute over (Å)} 10-60 {acute over (Å)} 20-40 Å (layer2): IR reflector  20-90 {acute over (Å)} 30-70 {acute over (Å)} 40-60 Å(e.g., NbZr) (layer 3): silicon nitride 300-800 {acute over (Å)} 400-700{acute over (Å)}  450-650 Å  (layer 4): IR reflector  20-90 {acute over(Å)} 25-70 {acute over (Å)} 35-55 Å (e.g., NbZr) (layer 5): siliconnitride 150-800 {acute over (Å)} 250-600 {acute over (Å)}  350-500 Å (layer 6): IR reflector  40-130 {acute over (Å)} 55-100 {acute over(Å)}  65-90 Å (e.g., NbZr) (layer 15): silicon nitride 100-700 {acuteover (Å)} 200-600 {acute over (Å)}  300-500 Å  (layer 16): overcoat 10-500 {acute over (Å)} 10-60 {acute over (Å)} 20-40 Å (e.g., ZrO₂)(layer 7):

Table 4 above relates to, for example, embodiments where glass sidereflective generally blue coloration and a low SF and/or SHGC value(s)are desirable for the FIG. 2 embodiment (or FIG. 2 embodiment used in anIG window unit as shown in FIG. 3) along with optical features discussedherein. It has been surprisingly found that in the FIG. 2 embodimentdesirable blue glass side reflective coloration can be achieved incombination with low SF and low SHGC values, and desirable film sidecolor and low glass side visible reflection using the thicknessesdiscussed in Table 4 above and when designing the FIG. 2 coating 8′ sothat one or more of the following are satisfied: (i) dielectric layer 4is thicker than dielectric layer 6 by at least 30 Å, more preferably byat least 50 Å; (ii) dielectric layer 16 is thicker than dielectric layer2 by at least 100 Å, more preferably by at least 200 Å; (iii) athickness ratio of layer 4/layer 2 is at least 2, more preferably atleast 4, and most preferably at least 5; (iv) thickness ratios of layer6/layer 2 and layer 16/layer 2 are each at least 2, more preferably atleast 3, and most preferably at least 4; (v) dielectric layer 4 isthicker than dielectric layer 16 by at least 50 Å, more preferably by atleast 100 Å; (vi) IR reflecting layer 15 is at 1.5 times as thick as IRreflecting layer 5; and (vii) IR reflecting layer 15 is at 1.25 times asthick as IR reflecting layer 3.

In certain example embodiments, the IR reflecting layers 3, 5 and 15 maybe of the same or substantially the same materials as indicated above(e.g., NbZr and/or a nitride thereof). In certain example embodiments,the layers 3, 5 and/or 15 are metallic, or substantially metallic, andare provided between nitride layers (e.g., silicon nitride based layers2, 4, 6, 16) in order to reduce or prevent oxidation of the IRreflecting layers during possible heat treatment (e.g., thermaltempering, heat bending, and/or heat strengthening) thereby permittingpredictable coloration to be achieved following the heat treatment atmultiple viewing angles.

Before and/or after any optional heat treatment (HT) such as thermaltempering, in certain example embodiments of this invention coatedarticles according to the FIG. 2 (or FIG. 2, 3) embodiment havecolor/optical characteristics as follows in Table 5 (measured monolithicand/or in an IG unit). Table 6 set forth below illustrates certaincharacteristics of coated articles according to certain exampleembodiments of this invention after HT such as thermal tempering(monolithically measured for Table 6) for all colors. Thecharacteristics below in Table 5 are applicable to HT and non-HT coatedarticles herein according to the FIG. 2 (or FIG. 2-3) embodiment, exceptthat the thermal stability data in Table 6 relates to HT coated articlesand demonstrates the stability upon HT.

TABLE 5 Color/Optical Characteristics (FIG. 2 embodiment monolithic orin IG) General Preferred Most Preferred T_(vis) (TY):    8-25%  10-18% 12-17% L*_(T) 30-60 35-55 40-50 a*_(T)  +5 to −16 +3 to −8 +2 to −4b*_(T) −15 to +15  −7 to +10 −3 to +4 R_(G/outside)Y(glass side): <=18%<=16% <=13% L*_(G) 20-60 25-50 30-40 a*_(G) −7 to +7 −5 to +5 −3 to +2b*_(G)  −8 to −30 −11 to −19 −12 to −18 R_(F/inside)Y(film side): <=25%<=20% <=16% a*_(F/inside)  −2 to +12  0 to +8 −+1 to +7  b*_(F/inside)−30 to +35 −15 to +30 −10 to +23 R_(s) (Ω/sq): <160    <100    30-75 SF[Monolithic]: <=0.35 <=0.33 <=0.31 SHGC [Monolithic]: <=0.40 <=0.38<=0.36 SF [IG]: <=0.25 <=0.23 <=0.22 or <=0.21 SHGC [IG]: <=0.27 <=0.25<=0.24

TABLE 6 Thermal Stability (FIG. 2 after HT; in addition to Table 5)General Preferred Most Preferred ΔE*_(G) <=4.0 <=3.5 <=3.0

For purposes of example only, Examples 1-2 representing differentexample embodiments of this invention, as well we Comparative Examples(CEs) 1-3, are set forth below.

EXAMPLES

Example 1 was a layer stack on a clear glass substrate as shown in FIG.1, and Example 2 was a layer stack on a clear glass substrate as shownin FIG. 2. Both were measured monolithically, heat treated and measuredagain. They were also put into IG window units as shown in FIG. 3. Thesilicon nitride layers in each example were deposited by sputtering asilicon target (doped with about 8% Al) in an atmosphere including argonand nitrogen gas. The glass substrates 1 and 30 were clear and 6 mmthick, and the air gap 34 in the IG window unit was 12 mm thick. TheNbZr layers in each example were deposited by sputtering approximately90/10 Nb/Zr magnetron sputtering targets in an atmosphere includingargon and a small amount of nitrogen gas. Comparative Examples (CEs) 1-3were provided for purposes of comparison. Layer thicknesses were inangstroms (Å), moving from the glass substrate outwardly.

TABLE 7 Layer Stacks of Examples Layer Ex. 1 Ex. 2 CE 1 CE 2 CE 3silicon nitride (layer 2): 764 Å  30 Å 485 Å 981 {acute over (Å)} 1310Å  NbZr (layer 3): 116 Å  50 Å  79 Å 310 {acute over (Å)} 107 Å siliconnitride (layer 4): 406 Å  525 Å  239 Å 144 {acute over (Å)} 236 Å NbZr(layer 5): 53 Å 44 Å 101 Å n/a n/a silicon nitride (layer 6): 60 Å 461Å  452 Å n/a n/a NbZr (layer 15): n/a 79 Å n/a n/a n/a silicon nitride(layer 16): n/a 360 Å  n/a n/a n/a ZrO₂ (layer 7): 30 Å 30 Å  40 Å  40{acute over (Å)}  40 Å

Measured monolithically before tempering (HT), Examples 1-2 according toembodiments of this invention and Comparative Examples (CEs) 1-3 had thefollowing characteristics (annealed and non-HT, monolithic) (Ill. C, 2degree observer). Note that “R_(G)Y(at angle of 45°)” indicates visibleglass side reflection at an angle of forty-five degrees from normal.

TABLE 8 Measured Monolithic, annealed (before tempering) Parameter Ex. 1Ex. 2 CE 1 CE 2 CE3 T_(vis) (TY) 16.8% 15.2% 22.5% 25.0% 34.0%(transmission): a*_(T) −0.9  −0.9 −3.0  −0.5 2.5 b*_(T) 7.1 −1.0 8.0 1.0 −8.0  R_(G)Y 14.9% 10.0% 13.0% 20.0% 26.0% (glass side refl. %):a*_(G): −0.1  −0.3 3.0 −4.0 −10.0  b*_(G): −14.2  −16.9  7.5 −16.5  3.0Glass side refl. blue blue bronze blue green color: R_(G)Y 13.9%  9.5%n/a n/a n/a (at angle of 45°): R_(F)Y 11.2%  8.2%  4.0% 27.5% 15.0%(film side refl. %): a*_(F): 7.9  1.8 30.0   2.5 0.0 b*_(F): 5.6 22.4−15.0  17.0 9.0 SF  0.308   0.298  0.337   0.411  0.513 (EN410-6732011): SHGC  0.351   0.341  0.388   0.472  0.590 (NFRC-2001):

It can be seen from Table 8 above that measured monolithically prior toany optional thermal tempering only Examples 1-2 had a combination ofdesirable blue glass side reflective visible color together with anacceptably low SF/SHGC value(s). It can be seen above that ComparativeExamples 1 and 3 (CEs 1 and 3) were undesirable at least because theycould not achieve blue glass side reflective coloration. And the only CEthat could achieve blue glass side reflective coloration was CE 2, butCE 2 was problematic in that its SF and SHGC values are too high(unacceptable). Surprisingly, it can be seen that the SF and SHGC valuesof Examples 1-2 were improved (lowered) relative to CE 2, even though CE2 had more (more total thickness) IR reflecting material, in that thetotal thickness of NbZr in CE 2 was greater than the total thickness ofNbZr in Examples 1 and 2. This is evidence of unexpected results. It canalso be seen from Table 8 that the SF and SHGC values of Examples 1-2were improved (lower) compared to those of CEs 1-3. It can also be seenthat the additional IR reflecting layer provided in Example 2 (comparedto Example 1) improved/lowered the glass side reflectance in a desirablemanner. It can also be seen that the glass side visible reflectance(R_(G)Y) of CEs 2-3 was undesirably higher compared to Examples 1-2.Accordingly, it can be seen that by providing two or more IR reflectinglayers (e.g., of or including NbZr and/or NbZrN_(x)) between respectivedielectric layers, along with particular thickness parameters, desirableblue glass side reflective coloration can be achieved together with lowglass side visible reflectivity, acceptable film side coloration, and alow SF/SHGC value(s). Thus, such coatings provide for improved colorcontrol and/or ranges when desired and low SF/SHGC value(s) indicatingability to keep rooms cool in warm environments.

Measured monolithically after tempering (HT), Examples 1-2 according toembodiments of this invention had the following characteristics (HT,monolithic) (Ill. C, 2 degree observer). The pre-HT data is provided inTable 9 for CEs 1-3, as it would not have significantly changed due toHT.

TABLE 9 Measured Monolithic, after thermal tempering (HT) for Exs. 1-2Parameter Ex. 1 Ex. 2 CE 1 CE 2 CE3 T_(vis) (TY) 15.8% 14.5% 22.5% 25.0%34.0% (transmission): a*_(T) −0.7  −0.2 −3.0  −0.5 2.5 b*_(T) 7.2 −0.58.0  1.0 −8.0  R_(G)Y 14.5%  9.3% 13.0% 20.0% 26.0% (glass side refl.%): a*_(G): 1.1  0.3 3.0 −4.0 −10.0  b*_(G): −12.4  −17.2  7.5 −16.5 3.0 Glass side refl. blue blue bronze blue green color: R_(G)Y 14.6%12.6% n/a n/a n/a (at angle of 45°): R_(F)Y 12.2% 10.9%  4.0% 27.5%15.0% (film side refl. %): a*_(F): 7.0 −0.1 30.0   2.5 0.0 b*_(F): 8.419.9 −15.0  17.0 9.0 SF  0.289   0.300  0.337   0.411  0.513 (EN410-6732011): SHGC  0.329   0.345  0.388   0.472  0.590 (NFRC-2001):

It can be seen from Table 9 above that following thermal tempering (HT)only Examples 1-2 had a combination of desirable blue glass sidereflective visible color together with an acceptably low SF/SHGCvalue(s). It can be seen above that Comparative Examples 1 and 3 (CEs 1and 3) were undesirable at least because they could not achieve blueglass side reflective coloration. And the only CE that could achieveblue glass side reflective coloration was CE 2, but CE 2 was problematicin that its SF and SHGC values are too high (unacceptable). It can alsobe seen from Table 9 that the SF and SHGC values of Examples 1-2 wereimproved (lower) compared to those of CEs 1-3. Accordingly, it can beseen that by providing two or more IR reflecting layers (e.g., of orincluding NbZr and/or NbZrN_(x)) between respective dielectric layers,along with particular thickness parameters, desirable blue glass sidereflective coloration can be achieved together with low glass sidevisible reflectivity, acceptable film side coloration, and a low SF/SHGCvalue(s). Thus, such coatings provide for improved color control and/orranges when desired and low SF/SHGC value(s) indicating ability to keeprooms cool in warm environments.

Measured in an IG window unit as shown in FIG. 3 (with the coating onsurface two) before tempering, Examples 1-2 according to embodiments ofthis invention and Comparative Examples (CEs) 1-3 had the followingcharacteristics (annealed and non-HT, IG unit) (Ill. C, 2 degreeobserver).

TABLE 10 IG Window Unit, annealed (before optional tempering) ParameterEx. 1 Ex. 2 CE 1 CE 2 CE3 T_(vis) (TY) 15.4% 13.7% 20.0% 23.0% 30.0%(transmission): a*_(T) −2.2  −1.9 −3.0  −1.0 2.0 b*_(T) 5.9 −0.5 7.5 1.2 −7.5  R_(G/out)Y 14.9% 10.4% 13.0% 20.0% 27.0% (glass side refl.%): a*_(G): 0.2 −1.7 3.0 −3.3 −10.0  b*_(G): −14.7  −16.9  9.0 −17.0 2.0 Glass side refl. blue blue bronze blue green color: R_(G)Y 14.5% 9.7% n/a n/a n/a (at angle of 45°): R_(F/interior)Y 16.6% 13.6% 10.0%27.0% 20.0% (film side refl. %): a*_(F): 3.5  0.2 10.0   1.0 −1.0 b*_(F): 2.8  9.9 −9.0  12.3 5.0 SF  0.209   0.202  0.230   0.280  0.350(EN410-673 2011): SHGC  0.239   0.233  0.265   0.322  0.403 (NFRC-2001):

It can again be seen from Table 10 above that measured in an IG windowunit as shown in FIG. 3 prior to any optional thermal tempering onlyExamples 1-2 had a combination of desirable blue glass side/outsidereflective visible color together with an acceptably low SF/SHGCvalue(s). It can be seen above that Comparative Examples 1 and 3 (CEs 1and 3) were undesirable at least because they could not achieve blueglass side reflective coloration. And the only CE that could achieveblue glass side reflective coloration was CE 2, but CE 2 was problematicin that its SF and SHGC values are too high (unacceptable). It can alsobe seen from Table 10 that the SF and SHGC values of Examples 1-2 wereimproved (lower) compared to those of CEs 1-3. Accordingly, it can beseen that by providing two or more IR reflecting layers (e.g., of orincluding NbZr and/or NbZrN_(x)) between respective dielectric layers,along with particular thickness parameters, desirable blue glass sidereflective coloration can be achieved together with low glass sidevisible reflectivity, acceptable film side coloration, and a low SF/SHGCvalue(s). Thus, such coatings provide for improved color control and/orranges when desired and low SF/SHGC value(s) indicating ability to keeprooms cool in warm environments.

Measured in an IG window unit after tempering (HT), Examples 1-2according to embodiments of this invention had the followingcharacteristics (HT, IG unit) (Ill. C, 2 degree observer). The pre-HT IGunit data is provided in Table 11 for CEs 1-3, as it would not havesignificantly changed due to HT.

TABLE 11 IG Window Unit, after thermal tempering (HT) for Exs. 1-2Parameter Ex. 1 Ex. 2 CE 1 CE 2 CE3 T_(vis) (TY) 14.6% 12.6% 20.0% 23.0%30.0% (transmission): a*_(T) −1.7  −1.3 −3.0  −1.0 2.0 b*_(T) 8.3  0.47.5  1.2 −7.5  R_(G/out)Y 14.9% 10.6% 13.0% 20.0% 27.0% (glass siderefl. %): a*_(G): 1.2 −1.6 3.0 −3.3 −10.0  b*_(G): −13.1  −16.2  9.0−17.0  2.0 Glass side refl. blue blue bronze blue green color: R_(G)Y14.6%  9.9% n/a n/a n/a (at angle of 45°): R_(F/interior)Y 17.3% 15.3%10.0% 27.0% 20.0% (film side refl. %): a*_(F): 3.2 −0.9 10.0   1.0 −1.0 b*_(F): 5.2 11.5 −9.0  12.3 5.0 SF  0.215   0.209  0.230   0.280  0.350(EN410-673 2011): SHGC  0.249   0.244  0.265   0.322  0.403 (NFRC-2001):

It can again be seen from Table 11 above that following thermaltempering (HT) in an IG window unit only Examples 1-2 had a combinationof desirable blue glass side/outside reflective visible color togetherwith acceptably low SF/SHGC value(s). It can be seen above thatComparative Examples 1 and 3 (CEs 1 and 3) were undesirable at leastbecause they could not achieve blue glass side reflective coloration.And the only CE that could achieve blue glass side reflective colorationwas CE 2, but CE 2 was problematic in that its SF and SHGC values aretoo high (unacceptable). It can also be seen from Table 11 that the SFvalues (and thus the SHGC values) of Examples 1-2 were improved (lower)compared to those of CEs 1-3. Accordingly, it can be seen that byproviding two or more IR reflecting layers (e.g., of or including NbZrand/or NbZrN_(x)) between respective dielectric layers, along withparticular thickness parameters, desirable blue glass side reflectivecoloration can be achieved together with low glass side visiblereflectivity, acceptable film side coloration, and a low SF/SHGCvalue(s). Thus, such coatings provide for improved color control and/orranges when desired and low SF/SHGC value(s) indicating ability to keeprooms cool in warm environments.

Example 3

Example 3 was similar to Example 2 with respect to the layer stack, asshown in FIG. 2. Example 3 was as follows: glass (5.8 mm clear)/Si3Nx(10 nm)/NbZr (5.3 nm)/Si3Nx (57.4 nm)/NbZr (4.2 nm)/Si3Nx (40 nm)/NbZr(7.1 nm)/Si3Nx (42 nm)/ZrOx (3 nm). Example 3 has SF and SHGC valuessimilar to Example 2 above, realized glass side reflective blue color,and had the following optical characteristics as coated (prior tothermal tempering): TY 15.0%; a*_(T)−1.0; b*_(T)−1.0; R_(G/out)Y 10.5%;a*_(G)−1.4; b*_(G)−18.0; R_(F/interior) 5.0%; a*F 7.0; and b*F 29.0.Example 3 following thermal tempering (heat treatment) had the followingoptical characteristics: TY 14.0%; a*_(T)−0.5; b*_(T)−2.5; R_(G/out)Y10.5%; a*_(G)−0.5; b*_(G)−18.0; R_(F/interior) 5.0%; a*_(F) 5.0; and b*F30.0.

It is noted above that one, two or all of IR reflecting layers 3, 5, 15may be of or include NiCrMo and/or NiCrMoN_(x), in certain exampleembodiments of this invention. In such embodiments one, two or all ofthe IR reflecting layers 3, 5, 15 may, for example, be of or include C22or an oxide and/or nitride thereof. Table 12 below shows an examplecomposition of the NiCrMo-based alloy C22.

TABLE 12 NiCrMo based alloy C22 (wt. %) Element Preferred More PreferredExample Ni 40-70%  50-60%  54-58% (e.g., 56%)  Cr 5-40% 10-30%   20-22.5% Mo 5-30% 10-20%  12.5-14.5% Fe 0-15% 0-10% 1-5% (e.g., 3%) W0-15% 0-10% 1-5% (e.g., 3%) Co 0-15% 0-10% 1-5% (e.g., 3%) Si  0-2% 0-1% =<0.2% (e.g., .08%)  Mn  0-3%  0-2%  =<1% (e.g., 0.5%) C  0-1%0-0.5%  =<0.1% (e.g., .01%)  V  0-2%  0-1%  =<1% (e.g., 0.35%)

Once given the above disclosure many other features, modifications andimprovements will become apparent to the skilled artisan. Such otherfeatures, modifications and improvements are therefore considered to bea part of this invention, the scope of which is to be determined by thefollowing claims:

What is claimed is:
 1. A coated article having blue glass side reflective coloration and including a layer system supported by a glass substrate, the layer system comprising: a first dielectric layer comprising silicon nitride; a first infrared (IR) reflecting layer comprising NbZr on the glass substrate over at least the first dielectric layer comprising silicon nitride; a second dielectric layer comprising silicon nitride on the glass substrate over at least the first dielectric layer comprising silicon nitride and the first IR reflecting layer comprising NbZr; a second layer IR reflecting layer comprising NbZr on the glass substrate over at least the second dielectric layer comprising silicon nitride; wherein the second dielectric layer comprising silicon nitride is located directly between and contacting the first and second IR reflecting layers comprising NbZr; a third dielectric layer comprising silicon nitride on the glass substrate over at least the second IR reflecting layer comprising NbZr; wherein the coated article contains no metallic infrared (IR) reflecting layer based on Ag and/or Au, and wherein the IR reflecting layers do not physically contact any other metallic or substantially metallic layer; and wherein the coated article: has glass side visible reflectance of no greater than 18%, a film side/interior reflective a* color value of −2 to +12, glass side/exterior reflective blue coloration comprising a glass side/exterior b* color value of from −8.0 to −30.0; and (i) if measured monolithically has an SF value of no greater than 0.35 and an SHGC value of no greater than 0.40, and/or (ii) if an insulating glass (IG) window unit having two glass substrates has an SF value of no greater than 0.25 and an SHGC value of no greater than 0.27.
 2. The coated article of claim 1, wherein the coated article has a glass side/exterior b* value of from −11.0 to −19.0.
 3. The coated article of claim 1, wherein the coated article has a glass side/exterior a* value of from −7.0 to +7.0.
 4. The coated article of claim 1, wherein the coated article (i) if measured monolithically has an SF value of no greater than 0.33 and an SHGC value of no greater than 0.38, and/or (ii) if an insulating glass (IG) window unit having two glass substrates has an SF value of no greater than 0.23 and an SHGC value of no greater than 0.25.
 5. The coated article of claim 1, wherein the coated article has a film side/interior reflective a* value of from 0 to +8.0.
 6. The coated article of claim 1, wherein at least one of the first and second IR reflecting layers comprising NbZr are nitrided.
 7. The coated article of claim 1, wherein each of the first and second IR reflecting layers comprising NbZr includes more Nb than Zr based on an atomic percentage.
 8. The coated article of claim 1, wherein the coated article is heat treated and has a ΔE* value (glass side reflective) of no greater than 3.0 after and/or due to heat treatment.
 9. The coated article of claim 1, wherein the coated article has a visible transmission of from 10-18%.
 10. The coated article of claim 1, wherein at least one of the first and second layers IR reflecting layers is/are substantially free of oxygen.
 11. The coated article of claim 1, wherein the coating further comprising an overcoat layer comprising an oxide of zirconium.
 12. The coated article of claim 1, wherein the coating includes only two IR reflecting layers and consists essentially of the first dielectric layer comprising silicon nitride, the first infrared (IR) reflecting layer comprising NbZr, the second dielectric layer comprising silicon nitride, the second layer IR reflecting layer comprising NbZr, and third dielectric layer comprising silicon nitride, and optionally an overcoat layer comprising an oxide of zirconium.
 13. The coated article of claim 1, wherein the first dielectric layer is thicker than the second dielectric layer by at least 100 Å.
 14. The coated article of claim 1, wherein the second dielectric layer is thicker than the third dielectric layer by at least 100 Å.
 15. The coated article of claim 1, wherein a thickness ratio of the first dielectric layer/third layer is at least
 5. 16. The coated article of claim 1, wherein the first IR reflecting layer is thicker than the second IR reflecting layer by at least 20 Å.
 17. The coated article of claim 1, wherein the coating further comprises: a third IR reflecting layer comprising NbZr on the glass substrate over at least the third dielectric layer comprising silicon nitride; and a fourth dielectric layer comprising silicon nitride on the glass substrate over at least the third IR reflecting layer comprising NbZr.
 18. The coated article of claim 1, wherein the coating has two or more of the following features: (a) a thickness ratio of the third dielectric layer/first dielectric layer is at least 2; (b) a thickness ratio of the fourth dielectric layer/first dielectric layer is at least 2; (c) the second dielectric layer is thicker than the fourth dielectric layer by at least 50 Å; (d) the third IR reflecting layer is at least 1.5 times as thick as the second IR reflecting layer; and (e) the third IR reflecting layer is at least 1.25 times as thick as the first IR reflecting layer.
 19. The coated article of claim 1, wherein the coating has three or more of the following features: (a) a thickness ratio of the third dielectric layer/first dielectric layer is at least 2; (b) a thickness ratio of the fourth dielectric layer/first dielectric layer is at least 2; (c) the second dielectric layer is thicker than the fourth dielectric layer by at least 50 Å; (d) the third IR reflecting layer is at least 1.5 times as thick as the second IR reflecting layer; and (e) the third IR reflecting layer is at least 1.25 times as thick as the first IR reflecting layer.
 20. A coated article having blue glass side reflective coloration and including a layer system supported by a glass substrate, the layer system comprising: a first dielectric layer comprising nitrogen; a first infrared (IR) reflecting layer on the glass substrate over at least the first dielectric layer; a second dielectric layer comprising nitrogen on the glass substrate over at least the first dielectric layer and the first IR reflecting layer; a second layer IR reflecting layer on the glass substrate over at least the second dielectric layer; a third dielectric layer comprising nitrogen on the glass substrate over at least the second IR reflecting layer; wherein each of the first and second IR reflecting layers comprises one or more of: NbZr, NbZrN_(x), NiCr, NiCrN_(x), NiCrMo, NiCrMoN_(x), NbCr, NbCrN_(x), Nb and NbN_(x); wherein the coated article contains no metallic infrared (IR) reflecting layer based on Ag and/or Au, and wherein the IR reflecting layers do not physically contact any other metallic or substantially metallic layer; and wherein the coated article: has glass side visible reflectance of no greater than 18%, a film side/interior reflective a* color value of −2 to +12, glass side/exterior reflective blue coloration comprising a glass side/exterior b* color value of from −8.0 to −30.0; and (i) if measured monolithically has an SF value of no greater than 0.35 and an SHGC value of no greater than 0.40, and/or (ii) if an insulating glass (IG) window unit having two glass substrates has an SF value of no greater than 0.25 and an SHGC value of no greater than 0.27. 